There has been recently developed a hybrid electric rotary excavator of which rotary body is driven by an electric actuator such as an electric motor while a work equipment and a carriage thereof are driven by a hydraulic actuator.
Since the rotation of the rotary body of such an electric rotary excavator is effected by the electric actuator, even when the rotary body is rotated while a boom and an arm that are hydraulically driven are moved up and down, the rotation of the rotary body is hardly affected by the up-down movement of the boom and the arm. Thus, as compared to a conventional excavator of which rotary body is hydraulically driven, the loss in the control valve and the like can be reduced to enhance the energy efficiency.
Since most of the operators are accustomed to an operation of the conventional excavator of which rotary body is hydraulically driven, the operators may feel uncomfortable during operation due to the behavior of such an electric rotary excavator different from the rotary action of the conventional excavator. Accordingly, there is a demand for providing an excavator that provides similar operation feeling irrespective of the difference in the drive system of the rotary body (i.e. electric drive or hydraulic drive).
In view of the above, an electric rotary excavator has been proposed, in which a torque current command corresponding to a operation amount of a control lever in operating the control lever is generated, a correction torque current command corresponding to the operation amount of the control lever and a rotary speed of the rotary body is generated, and a drive command is generated based on the correction torque current command in order to bring the operation feeling closer to that of a hydraulically driven excavator (see, for instance, Patent Literature 1).
In another excavator, a redundant control command is generated upon operating a rotation control lever of an electric rotary excavator to appropriately control an operation of a rotary body (see, for instance, Patent Literature 2).